Mobile electronic devices are increasingly used in both business and personal environments for e.g. communication and entertainment. Examples of such devices are mobile phones, smart phones and music players. Such mobile devices are provided with a battery for storing energy. If these mobile devices are also provided with a coil, particularly a secondary coil, the battery can be charged or recharged by means of an inductive battery charger. A prior art charger comprises a base station having a horizontally oriented flat supporting surface for supporting the mobile device to be charged or recharged. A primary coil or a primary coil array is accommodated in the base station, as well as the necessary electronics for energizing the primary coil or coil array. Wireless power transfer is enabled by positioning the mobile device on the supporting surface, in such a way that the secondary coil of the mobile device faces the supporting surface of the base station, wherein the supporting constitutes a charging area.
A drawback of the known charger is that wireless charging can not occur when the mobile device is positioned upside down on the supporting surface of the base station, because in that situation the secondary coil of the mobile device is at a too large distance to the primary coil or coil array of the base station for making an inductive coupling.